Deficits in striatal dopamine release in cannabis dependence

Area of Science:

• Neuroscience
• Addiction Research
• Psychopharmacology

Background:

• Drugs of abuse often impair dopamine release, contributing to dependence and poor outcomes.
• Cannabis dependence may similarly affect dopamine systems, but evidence is limited, especially in individuals without comorbidities.

Purpose of the Study:

• To investigate whether severe cannabis dependence (CD) is associated with deficits in striatal and extrastriatal dopamine release.
• To explore correlations between dopamine release, glutamate levels, psychopathology, and neurocognition in cannabis-dependent individuals.

Main Methods:

• Positron emission tomography (PET) scans with [11C]-(+)-PHNO were used to measure dopamine release in 11 CD participants and 12 healthy controls (HC).
• d-amphetamine was administered to assess changes in dopamine release (ΔBPND).
• Magnetic resonance spectroscopy (MRS) measured glutamate levels; neurocognitive and psychopathological assessments were also performed.

Main Results:

• Cannabis-dependent individuals exhibited significantly lower dopamine release in the striatum, including associative and sensorimotor regions, and the pallidus.
• Reduced associative striatal dopamine release correlated with inattention, negative symptoms, and poorer working memory and category learning in both CD and HC groups.

Conclusions:

• Severe cannabis dependence, even without comorbidities, is associated with a deficit in striatal dopamine release.
• This dopamine deficit extends to extrastriatal areas and is linked to psychopathological and neurocognitive impairments.